1. Field of the Invention
The present invention relates to a solid-state imaging device and, more specifically, to a technique of improving signal output characteristics from a light receiving element.
2. Description of the Background Art
A CMOS (Complementary Metal Oxide Semiconductor) image sensor as one type of solid-state imaging device utilizes a configuration in which charges from pixels including light receiving elements are transferred to a floating diffusion and a potential of the floating diffusion is read using a source-follower amplifier.
By way of example, Japanese Patent Laying-Open No. 2005-311487 (JP 2005-311487A) describes a configuration of a solid-state imaging device including: a light receiving element (photo-diode); an MOS transistor for transfer, receiving a row selection signal at its gate; an MOS transistor for resetting the potential of floating diffusion; and an amplifying transistor for forming the source-follower amplifier with a constant current source outside of the pixels. In the solid-state imaging device described in JP 2005-311487A, a differential transistor forming a differential pair with the amplifying transistor in the pixel is connected through a signal line to which a signal is output from a unit pixel, and an output signal from the pixel is derived from the differential transistor. This enables improved dynamic range and linearity.